In the field of power electronics, a high-voltage semiconductor device (power device) to which high voltage is applied is used.
For example, Patent Document 1 discloses an SiC vertical MOSFET including an n drift layer laminated on an n+ drain layer, a p base region formed on a surface layer of the n drift layer, an n+ source region formed in the p base region, a high-concentration p+ well region formed to overlap the p base region, a gate electrode layer provided, via a gate oxide film, on the surface of the p base region that is interposed between the n+ source region and an exposed surface portion of the n drift layer, a source electrode in contact commonly with the n+ source region and the p+ well region, a drain electrode provided on a back surface of the n+ drain layer, and an interlayer insulating film that insulates the gate electrode layer and the source electrode from each other.